Fortified city

A city, itself fortified, was the core of the fortress and within a protective ring of outer forts. Substantial garrisons typically manned the forts. The outer forts were sited to keep enemy artillery at such a distance that they could not strike the city the forts defended. By 1914 gun ranges had increased , and forts were inadequate to the new siege artillery such as the Krupp Big Bertha and Skoda, howitzers capable of throwing massive shells 50 miles or more.

Liége, Dinant, and Namur, the modern Belgian forts of the Meuse - were constructed of concrete and steel with low profiles and domed roofs. Shells fired on a low arc that struck the roof were deflected with little damage, but howitzers fired shells on a high arc, so they dropped down upon the roof, causing heavy damage. The port of Antwerp was the last Belgian fortified city to fall.

Russian forts, like Ivangorod, were constructed of brick and outdated by 1914. Ivangorod survived Germany's shortlived invasion of Russian Poland in 1914, but fell in the Gorlice-Tarnow Offensive. On August 10, 1915, the great Russian fortress at Novo-Georgievsk was besieged. Its garrison surrendered ten days later with 190,000 Russian prisoners.

The great Austro-Hungarian fortresses of Lemberg and Przemyśl both fell. The Russians took 120,000 prisoners at Przemyśl.

The French fortress at Maubeuge fell on September 7, 1914 after a two-week seige even as the Allied victory of the Marne had begun. After the fall of the Allied forts, French commander Joffre put little value in them, and stripped Verdun of its guns prior to the German siege in 1916. The government forced him to hold the city. Verdun was a fortified city that held, at great cost to the defending French and the besieging Germans.